Brier Score Calculator

Compute mean squared probability error for binary outcomes. Probabilities must lie in [0,1], outcomes must be 0 or 1; lower scores are better.

Description

Compute mean squared probability error for binary outcomes. Probabilities must lie in [0,1], outcomes must be 0 or 1; lower scores are better.

Brier Score Calculator: Compute mean squared probability error for binary outcomes. Probabilities must lie in [0,1], outcomes must be 0 or 1; lower scores are better.

When to use Brier Score

Use this metric to quantify prediction error or classification quality only after matching the target scale, aggregation, weighting, and statistical assumptions to the evaluation question.

probabilities
Required list input.
outcomes
Required list input.

How Brier Score works

Compute mean squared probability error for binary outcomes. Probabilities must lie in [0,1], outcomes must be 0 or 1; lower scores are better. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.1

score
The resulting score returned as a number.

Limitations and assumptions

  • Different metrics penalize errors differently and can be dominated by outliers, scale, imbalance, zeros, or threshold choices. A single aggregate hides subgroup, temporal, and distributional failures.
  • Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Alternative or Complementary approaches

Report multiple complementary metrics with uncertainty and subgroup breakdowns, inspect residuals, and compare against meaningful baselines.

References

  1. Brier score — Wikipedia contributors

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